ACS GEOIDs

Hey All,

I am using the 5-year (2015-2019) ACS data accessed via the census API. Do the GEOIDs in the ACS 2015-2019 correspond to 2010 census tracts or 2020 tracts? Something else? Will this change for 2016-2020 5-year ACS data?

Thanks for your help in advance.

Best,

James